Modified polymer having organic group derived from compound having mono-nitroxide free radical

ABSTRACT

A process for producing a modified polymer having, in the molecule thereof, an organic group(s) introduced thereinto and derived from a compound(s) having a free radical comprising reacting a polymer such as an elastomer with a compound having the free radical stable at an ordinary temperature in the presence of oxygen, after or while a carbon radical(s) is generated in the polymer, whereby the modified polymer having an improved bondability and processability is formed.

TECHNICAL FIELD

The present invention relates to a process for producing a modifiedpolymer, more particularly it relates to a process for producing amodified polymer by reacting a polymer such as an elastomer with acompound(s) having a free radical or radicals stable in the presence ofoxygen at ordinary temperature (hereinafter referred to as “stable freeradical”).

BACKGROUND ART

For example, as disclosed in Japanese Unexamined Patent Publication(Kokai) No. 10-182881, it has been proposed to compound stable freeradicals such as TEMPO (i.e., 2,2,6,6-tetramethyl-1-piperidinyloxy) intorubber to improve the physical properties of the rubber composition, inparticular those such as processability, abrasion resistance. Further,Japanese Unexamined Patent Publication (Kokai) No. 8-239510 proposes toinclude a TEMPO derivative in a polymer to prevent polymer aging.However, no reference can be found relating to positively the generationof carbon radical or radicals in polymers such as rubbers so as tomodify polymers using a compound(s) having a stable free radical or theradicals in the molecule thereof.

DISCLOSURE OF THE INVENTION

Accordingly, the object of the present invention is to modify a polymersuch as an elastomer to improve the bondability (or adhesion) andprocessability of the polymer.

In accordance with the present invention, there is proposed a processfor producing a modified polymer having, in the molecule thereof, anorganic group or groups introduced thereinto and derived from acompound(s) having a free radical or the radicals comprising reacting apolymer with a compound(s) having the free radical or radicals stable atan ordinary temperature in the presence of oxygen, after or while acarbon radical or radicals are generated in the polymer.

BEST MODE FOR CARRYING OUT THE INVENTION

Compounds having a stable free radical or the radicals such as TEMPOquickly trap radicals produced by the cleavage of rubber by light, heat,or mechanical action. However, if trying to introduce functional groupsinto the molecules of an elastomer, it is not possible to sufficientlymodify the elastomer with only a compound having stable free radicalssuch as TEMPO. Therefore, the inventors succeeded in introducing thedesired functional groups into elastomer molecules by positively causingthe generation of carbon radicals on the polymer molecular chainswhereby the present invention has been completed.

As polymers capable of being modified according to the presentinvention, for example, diene-based rubbers such as natural rubbers(NR), polyisoprene rubbers (IR), various types of styrene-butadienecopolymer rubbers (SBR), various types of polybutadiene rubbers (BR),acrylonitrile butadiene copolymer rubbers (NBR), butyl rubbers (IIR),chloroprene rubbers (CR); olefin-based rubbers such asethylene-propylene copolymer rubbers (EPM, EPDM), chlorosulfonatedpolyethylenes (CSM), epichlorohydrin rubbers (CO, ECO), acryl rubbers(ACM, ANM) and, polysulfide rubbers (OT) may be illustrated. Further, asthermoplastic elastomers capable of being modified according to thepresent invention, polystyrene-based TPE (SBS, SIS, SEBS),polyolefin-based TPE, polyvinyl chloride-based TPE, polyurethane-basedTPE, polyester-based TPE, polyurethane-based TPE, polyamide-based TPE,etc. may be illustrated. Further, as a polyolefin capable of beingmodified according to the present invention, for example, polyethylene(PE), polypropylene (PP), polyvinyl chloride (PVC), chlorinated polymers(CPE, CPP), polystyrene (PS), styrene-acrylonitrile copolymer (SAN),acrylonitrile butadiene styrene (ABS), polyamide (PA), acetal resin(POM), polyphenylene oxide (PPO), polyester, polycarbonate (PC),polysulfone, polyketone, polyacrylonitrile (PAN), polyimide (PI), liquidcrystal polymer (LCP), etc. may be mentioned.

On the other hand, as the compounds having, in the molecule thereof, afree radical or the radicals stable in the presence of oxygen atordinary temperature capable of being used in the present invention, thefollowing compounds may be illustrated.Nitroxide Radicals

2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)

4-oxoTEMPOGeneral Formula

In formulae (1) to (6), R indicates a C₁ to C₃₀ alkyl group, allylgroup, amino group, isocyanate group, hydroxy group, thiol group, vinylgroup, epoxy group, thiirane group, carboxyl group, carbonylgroup-containing group (e.g., cyclic acid anhydrides such as succinicanhydride, maleic anhydride, glutanic anhydride, phthalic anhydride,)organic groups containing functional groups an amide group, ester group,imide group, nitrile group, thiocyan group, C₁ to C₂₀ alkoxy group,silyl group, alkoxysilyl group, nitro group.

Further, other examples may be given as follows:

Hydrazyl Radical

Aryloxy Radical

Trityl Radical

In the present invention, as the means for generating a carbon radicalor radicals in the polymer, the method of adding a radical initiator tothe reaction system, the method of applying electron beams, light, heat,and radiation to the reaction system, etc. may be used. As the radicalinitiator, for example, organic peroxides such as benzoyl peroxide(BPO), t-butylperoxybenzoate (Z), dicumyl peroxide (DCP), t-butylcumylperoxide (C), t-butyl peroxide (D),2,5-dimethyl-2,5-di-t-butylperoxyhexane (2,5B),2,5-dimethyl-2,5-di-t-butylperoxy-3-hexyne (Hexyne-3),2,4-dichloro-benzoylperoxide (DC-BPO),di-t-butylperoxy-di-isopropylbenzene (P),1,1-bis(t-butylperoxy)-3,3,5-trimethyl-cyclohexane (3M),n-butyl=4,4-bis(t-butylperoxy)valerate, 2,2-bis(t-butylperoxy)butane,and azodicarbonamide (ADCA), azobisisobutylonitrile (AIBN),2,2′-azobis-(2-amidinopropane)dihydrochloride, dimethyl2,2′-azobis(isobutyrate), azobis-cyan valeric acid (ACVA),1,1′-azobis-(cyclohexane-1-carbonitrile) (ACHN),2,2′-azobis-(2,4-dimethylvaleronitrile) (ADVN), azobismethylbutylonitrile (AMBN), 2,2′-azobis-(4-methoxy-2,4-dimethylvaleronitrile),etc. may be mentioned. These radical generators can generate a carbonradical or radicals in a polymer by addition to a reaction system of thepolymer and compound having such stable free radicals (mixture system orcatalyzation system). The amount of the radical initiator added ispreferably, based upon 100 parts by weight of the polymer, 0.1 to 6.0parts by weight, more preferably 0.2 to 3.0 parts by weight.

According to the present invention, instead of the radical initiator orin addition to the radical initiator, it is possible to use an electronbeam (for example, β-rays), light (for example, UV light) and/orradiation (for example, γ-rays or X-rays) etc. to generate carbonradicals in the polymer.

According to the present invention, as the organic group or groupsintroduced into the polymer by the modification of the polymer, forexample, a C₁ to C₃₀ alkyl group, allyl group, amino group, isocyanategroup, hydroxyl group, thiol group, vinyl group, epoxy group, thiiranegroup, carboxyl group, carbonyl group-containing group (for example,cyclic acid anhydrides such as succinate anhydride, maleic anhydride,glutanic anhydride, phthalic anhydride; an amide group, ester group,imide group, nitrile group, thiocyan group, C₁ to C₂₀ alkoxy group,silyl group, alkoxysilyl group, etc. may be illustrated.

In addition to the modified polymer, polymers such as diene-basedrubbers, polyolefin-based rubbers, thermoplastic elastomer, polyolefins,various additives generally used for tire use or for other generalrubber use reinforcing fillers such as carbon black or silica,vulcanization or cross-linking agent, vulcanization or cross-linkingaccelerator, various types of oils, anti-aging agent, plasticizer may beblended in. The formulations are mixed and vulcanized to obtaincompositions by general methods and can be used for vulcanization orcross-linking. The amounts of these additives used may be made thegeneral amounts used in the past in so far as the object of the presentinvention is not adversely affected.

EXAMPLES

The present invention will now be explained by the following Examples,but, of course, the scope of the present invention is not limited tothese Examples.

Examples 1 to 2 and Comparative Examples 1 to 3 Synthesis of ModifyingTEMPO

50.68 g of tolylene diisocyanate (TDI made by Sumitomo Bayer UrethaneK.K.) was added to 50.0 g (0.291 mol) of OH-TEMPO (LA7RD made by AsahiDenka Kogyo K.K.) dissolved in 50 ml of acetone. The mixture wasagitated at room temperature for 24 hours. It was confirmed that theisocyanate content was 11.96% (theoretical value 12.13%). The acetonewas distilled off in vacuo, then the residue was dried to obtain thefinal product.

Production of Modified Polymer

Based on the formulations shown in Table I (parts by weight), a polymer(IR) and various compounding agents were mixed by means of rolls. Themixtures obtained were formed into sheets and heat treated in 150 mm×150mm×2 mm molds at 170° C. for 10 minutes to obtain modified polymers.However, Comparative Example 3 is a mixture of a polymer and variouscompounding agents by means of a roll, without heat treatment. TABLE IComp. Comp. Comp. Ex. 1 Ex. 2 Ex. 1 Ex. 2 Ex. 3 IR 100 100 100  100  100Modifying TEMPO 1 2 1 2 2 Radical 0.98 1.95 — — 1.95 initiatorModification 0.23 0.65 0 0 0 rate (wt %)(Notes)IR: Nipol IR-2200 (Nippon Zeon K.K.)Modifying TEMPOL: See above SynthesisRadical initiator: Percumyl D-40 (Nihon Oil & Fat K.K.)

Modification Rate

First, a calibration curve for finding the modification rate ofTDI-TEMPO on the polymer was prepared. Mixtures with different ratios ofIR rubber and the modifying TEMPO were uniformly dissolved in tolueneand the mixtures used for IR analysis. The calibration curve wasobtained by averaging the two peak ratios of the peak ratio of the peakof 1376 cm⁻¹ of the IR rubber to the peak of 1727 cm⁻¹ of the modifyingTEMPO and the peak ratio of the peak of 1448 cm⁻¹ of the IR rubber tothe peak of 1727 cm⁻¹ of the modifying TEMPO. Similarly, the peak ratiosof the modified polymers fabricated in Table I were calculated and thecalibration curves used to find the modification rates.

In Table I, Comparative Examples 1 and 2 have no peroxide added, andtherefore sufficient carbon radicals could not be generated in thepolymers and the polymers could not be modified with the modifyingTEMPO. In Comparative Example 3, peroxide was added, but no heattreatment was performed, and therefore sufficient carbon radicals couldnot be generated in the polymer and the rubber could not be modifiedwith the modifying TEMPO. In Examples 1 and 2, peroxide was added andheat treatment performed, and therefore sufficient carbon radicals weregenerated in the polymers and the polymers could be modified with themodifying TEMPO.

Examples 3 to 4 and Comparative Examples 4 to 5 Synthesis of ModifyingTEMPO

50.68 g of tolylene diisocyanate (TDI made by Sumitomo Bayer UrethaneK.K.) was added to 50.0 g (0.291 mol) of OH-TEMPO (LA7RD made by AsahiDenka Kogyo K.K.) dissolved in 50 ml of acetone. The mixture wasagitated at room temperature for 24 hours. It was confirmed that theisocyanate content was 11.96% (theoretical value 12.13%). The acetonewas distilled off in vacuo, then the residue was dried to obtain thefinal product.

Method of Preparation of Examples 3 to 4 and Comparative Examples 4 to 5Production of Modified Polymer

Based on the formulations shown in Table II (parts by weight), in Mixing1, the ingredients were mixed by a Bambury mixer adjusted to atemperature of 80° C. and the mixture discharged when reaching 140° C.to prepare a master batch. Next, in Mixing 2, the ingredients except forthe sulfur and vulcanization accelerator were mixed in a Bambury mixeradjusted to a temperature of 60° C. for 5 minutes, then a roll was usedto add the sulfur and vulcanization accelerator and obtain theunvulcanized rubber. TABLE II Comp. Comp. Ex. 3 Ex. 4 Ex. 4 Ex. 5 Mixing1 Formulation (parts by weight) IR 100 100 — — Modifying TEMPO 1.2 2.4 —— Radical initiator 0.98 1.95 — — NP total 102.18 104.35 — — Mixing 2Formulation (parts by weight) NP 102.18 104.35 — — IR — — 100 100Modifying TEMPO — — 1.2 2.4 Radical initiator — — 0.98 1.95 Carbon black60 60 60 60 Zinc white 3 3 3 3 Stearic acid 1 1 1 1 Antioxidant 1 1 1 1Aromatic oil 5 5 5 5 Sulfur 2.5 2.5 2.5 2.5 Vulcanization 1 1 1 1accelerator CZ Modification rate 0.35 0.51 0 0 (wt %) Bonding testPullout force (N) 75 87 12 14(Notes)IR: Nipol IR-2200 (made by Nippon Zeon K.K.)Radical initiator: Percumyl D-40 (Nihon Oil & Fat K.K.)Carbon black: HTC-100 (Chubu Carbon)Stearic acid: Beads Stearic Acid (Nihon Oil & Fat K.K.)Antioxidant: Nocrac 224 (Ouchi Shinko Chemical Industrial K.K.)Aromatic oil: Desolex No. 3 (Showa Shell Sekiyu K.K.)Sulfur: Oil extended sulfur (Karuizawa Refinery K.K.)Vulcanization accelerator CZ: Noccelar CZ-G (Ouchi ShinkoChemical Industrial K.K.)

Method of Fabrication of Bonding Test Samples and Test Method

Fiber cord (3300 dtex) composed of one type of polyester fiber, that is,polyethylene terephthalate fiber (PET), was dipped in a 2% aqueoussolution of an epoxy compound (diglycerol triglycidyl ether), dried at120° C. for one minute, then heat treated at 240° C. for 2 minutes. Thepolyester fiber cord thus treated was embedded in a predetermined lengthin the unvulcanized rubber which was then vulcanized at 150° C. for 30minutes to prepare a bonding test sample. The bonding test was based onthe JIS 1017 T-Test Method. The cord was pulled out from the sample andthe pullout force at that time was measured.

As shown in Table II, in a rubber composition using a master batch mixedby a Bambury mixer adjusted to a high temperature in Mixing 1,modification by the modifying TEMPO was confirmed. In this rubbercomposition, the bondability with the fiber was improved, but in rubbercompositions where modification was not confirmed, the bondability withthe fiber was not improved.

Examples 5 to 6 and Comparative Examples 6 to 7 Synthesis of ModifyingTEMPO

50.68 g of tolylene diisocyanate (TDI made by Sumitomo Bayer UrethaneK.K.) was added to 50.0 g (0.291 mol) of OH-TEMPO (LA7RD made by AsahiDenka Kogyo K.K.) dissolved in 50 ml of acetone. The mixture wasagitated at room temperature for 24 hours. It was confirmed that theisocyanate content was 11.96% (theoretical value 12.13%). The acetonewas distilled off in vacuo, then the residue was dried to obtain thefinal product.

Production of Modified Polymer

PP and the various compounding agents were mixed by anitrogen-substituted kneader at 200° C. for 15 minutes to obtain amodified polymer.

Modification Rate

A calibration curve for finding the modification rate of TDI-TEMPO onthe PP was prepared. Mixtures with different ratios of PP and modifyingTEMPO were prepared by kneaders and used for IR analysis. Thecalibration curve was obtained by averaging the two peak ratios of thepeak ratio of the peak of 1376 cm⁻¹ of PP with respect to the peak of1727 cm⁻¹ of the modifying TEMPO and the peak ratio of the peak of 1460cm⁻¹ of PP with respect to the peak of 1727 cm⁻¹ of the modifying TEMPO.Similarly, the peak ratios of the modified polymers fabricated in TableIII were calculated and the calibration curves used to find themodification rates. TABLE III Comp. Comp. Ex. 5 Ex. 6 Ex. 6 Ex. 7Formulation (parts by weight) PP 100 100 100 100 Modifying TEMPO 1 2 1 2DCP 0.5 1 — — Modification rate 0.31 0.55 0 0 (wt %)(Notes)PP: Polypropylene (made by Sumitomo Chemical K.K.)Modifying TEMPO: See above SynthesisDCP: Dicumyl peroxide (Aldrich Chemical K.K.)

As shown in Table III, in Examples 5 and 6, modification of the polymerwas confirmed in samples adding modifying TEMPO and peroxide to PP andmixing them at a high temperature. In Comparative Examples 6 and 7,peroxide was not added, and therefore the PP could not be modified.

INDUSTRIAL APPLICABILITY

According to the present invention, by modifying a polymer, thebondability and processability can be improved and the polymer can beeffectively used for rubber products such as tires, conveyor belts,hoses, and also as plastic products.

1-5. (canceled)
 6. A modified polymer comprising an organic groupderived from a compound(s) having a mono-nitroxide free radical(s),wherein said modified polymer is obtained by (1) generating a carbonradical(s) in the molecule of a polymer to be modified by at least onemeans for generating a carbon radical selected from the group consistingof a radical initiator, electron beam, light and radiation, and (2)reacting the polymer having the carbon radical(s) generated above with acompound(s) having the mono-nitroxide free radical stable at an ordinarytemperature in the presence of oxygen.
 7. The modified polymer asclaimed in claim 6, wherein said organic group is at least one groupselected from the group consisting of a C₁ to C₃₀ alkyl group, allylgroup, amino group, isocyanate group, hydroxyl group, thiol group, vinylgroup, epoxy group, thiirane group, carboxyl group, carbonyl-groupcontaining group, amide group, ester group, imide group, nitrile group,thiocyan group, C₁ to C₂₀ alkoxy group, silyl group and alkoxysilylgroup.
 8. The modified polymer as claimed in claim 6, wherein a meansfor generating a carbon radical is the use of a radical initiator. 9.The modified polymer as claimed in claim 8, wherein the amount of use ofthe radical initiator is 0.1 to 0.6 parts by weight based upon 100 partsby weight of said polymer.
 10. The modified polymer as claimed in claim6, wherein the generation of the carbon radical is carried out in thepresence of the compound(s) having the mono-nitroxide free radicals.